Tubing of this kind, known from German Pat. No. 12 18 574, is used in electrical installation. It is fastened by nails, the nail being driven through the web and forming a hole in the area between two opposed hollows in the corrugation. There is a very great danger that the web will tear here. This is not important in the above-mentioned use of the known double tubing, but if double tubing of this kind is to be used for plumbing purposes, care must be taken to assure that it cannot become damaged while being installed.
German Pat. No. 20 38 991 discloses the use of a protective tube, embodied as a corrugated tube, as a shared protective tube for a hot water flow line and return line to and from radiators.
It is also known to secure plastic protective tubes to the floor or walls by means of ring clamps, these protective tubes receiving elastic tubes for plumbing purposes, in particular for flow and return lines for heating systems.